charsets: fix handling of 0x00 bytes at the end of GSM encoded strings

When a GSM-7 encoded string is packed, the process of packing the
septets into bytes may end up with one last byte holding the last bit
of the last septet. When this situation happens, the last byte will
end up with the 7 remaining bits set to 0.

When this packed string is unpacked, the logic to unpack will unpack
those last 7 bits as an additional septet, with the value 0x00.

The 0x00 value encoded in GSM-7 is the '@' character, EXCEPT when this
character is found at the end of the string, in which case the value
should be considered as NUL and trigger the end of string already.

So, fix the conversion logic between GSM-7 and UTF-8, so that whenever
we find the 0x00 character at the end of the string, we ignore it
instead of adding a bogus '@' trailing character.

This commit fixes the "/MM/charsets/gsm7/default-chars" unit test
after having it updated to perform the full conversion cycle:
   UTF-8 -> packed GSM7 -> UTF-8

0 files changed, 0 insertions, 0 deletions